I can see the problem here. You are seeing a form with purple branding and some drop down lists (see the question's edit history) that looks something like this...
But for the situation you have described, you want a Standard Visitor Visa, and the correct form looks like this...
So the bottom line is that you are filling out the wrong form.
The Gateway for the Standard Visitor Visa is at Apply for a UK Visa, and the welcome page looks like this...
Once you begin filling out the form, you will see that the branding is different and the questions prefer radio buttons as opposed to drop-down lists. They changed the forms earlier this year and the migration process continues.
Why are there two different forms? The old form had problems, perhaps the largest problem is that it did not acknowledge the existence of the Standard Visitor Visa. It also asked questions that should not be asked of visitors like "Do you know anyone in the UK?". So they made a separate form. They did this in conjunction with external members of the public to assure that they wouldn't have a flood of complaints and that all the various requirements were adequately represented. The similar questions exist on the old form because... well because UKVI takes a long time to rationalise their various forms.
Once you begin filling out the form, you'll see that it's much more straight-forward and amenable to those seeking a Standard Visitor Visa.
To repeat, the correct form is at Apply for a UK Visa.
